1. Field of the Invention:
The present invention relates to a sunlight shielding translucent glass panel having a multilayer film structure including a film composed mainly of silver (Ag), and a sunlight shielding translucent multilayer glass panel assembly which includes such a sunlight-shielding translucent glass panel.
2. Description of the Related Art:
Recent years have seen widespread use of multilayer window glass panes to meet growing demands for highly air-tight, thermally insulated houses. For the purpose of increasing thermal insulating performance and sunlight shielding performance, multilayer glass panes using a glass sheet which has a multilayer film structure including a film composed mainly of Ag are also finding popular use. If multilayer glass panes using a glass sheet which has a multilayer film structure including a mainly Ag film are employed as window glass panes, then the windows have improved thermal insulating performance and sunlight shielding performance. The improved thermal insulating performance cuts down on the cost of heating the house in winter-time, and the improved sunlight shielding performance reduces the cost of cooling the house in summertime.
On conventional glass panel having a multilayer film structure including a mainly Ag film is disclosed in Japanese patent publication No. 7-15143, for example. As shown in FIG. 1 of the accompanying drawings, the disclosed glass panel comprises a transparent glass sheet 11, a first transparent dielectric film 13 disposed on the transparent glass sheet 11, a mainly Ag film 15 disposed on the first transparent dielectric film 13, and a second transparent dielectric film 17 disposed on the mainly Ag film 15. A multilayer film structure composed of the three films 13, 15, 17 will be referred to as a single-Ag-layer LowE film structure.
Another known glass panel having a multilayer film structure including mainly Ag films is also disclosed in Japanese patent publication No. 7-165442. As shown in FIG. 2 of the accompanying drawings, the disclosed glass panel comprises a transparent glass sheet 11, a first transparent dielectric film 13 disposed on the transparent glass sheet 11, a first mainly Ag film 15 disposed on the first transparent dielectric film 13, a second transparent dielectric film 17 disposed on the first mainly Ag film 15, a second mainly Ag film 19 disposed on the second transparent dielectric film 17, and a third transparent dielectric film 21 disposed on the second mainly Ag film 19. A multilayer film structure composed of the five films 13, 15, 17, 19, 21 will be referred to as a double-Ag-layer LowE film structure.
Still another known glass panel having a multilayer film structure including mainly Ag films is disclosed in Japanese patent publication No. 7-149545. As shown in FIG. 3 of the accompanying drawings, the disclosed glass panel comprises a transparent glass sheet 11, a first transparent dielectric film 13 disposed on the transparent glass sheet 11, a first mainly Ag film 15 disposed on the first transparent dielectric film 13, a second transparent dielectric film 17 disposed on the mainly Ag film 15, a second mainly Ag film 19 disposed on the second transparent dielectric film 17, a third transparent dielectric film 21 disposed on the second mainly Ag film 19, a third mainly Ag film 23 disposed on the third transparent dielectric film 21, and a fourth transparent dielectric film 25 disposed on the third mainly Ag film 23. A multilayer film structure composed of the seven films 13, 15, 17, 19, 21, 23, 25 will be referred to as a triple-Ag-layer LowE film structure.
A comparison between the double-Ag-layer LowE film structure and the single-Ag-layer LowE film structure which have the same visible light transmittance indicates that the double-Ag-layer LowE film structure is better than the single-Ag-layer LowE film structure with respect to the sunlight shielding performance. Therefore, a window glass pane which comprises a multilayer glass pane that employs the glass panel with the double-Ag-layer LowE film structure is more effective in suppressing a rise in the indoor temperature than a window glass pane which comprises a multilayer glass pane that employs the glass panel with the single-Ag-layer LowE film structure, whereas both window glass panels ensure substantially the same indoor lightness during the daytime.
A comparison between the triple-Ag-layer LowE film structure and the double-Ag-layer LowE film structure which have the same visible light transmittance indicates that the triple-Ag-layer LowE film structure is better than the double-Ag-layer LowE film structure with respect to the sunlight shielding performance. A window glass pane which comprises a multilayer glass pane that employs the glass panel with the triple-Ag-layer LowE film structure is more effective in suppressing a sunlight-induced rise in the indoor temperature while keeping the room light during the daytime, and also in reducing the load on the air-conditioning unit, than a window glass pane which comprises a multilayer glass pane that employs the glass panel with the double-Ag-layer LowE film structure.
However, the double-Ag-layer LowE film structure is more expensive than the single-Ag-layer LowE film structure as the former has more films than the latter. Similarly, the triple-Ag-layer LowE film structure is more expensive than the double-Ag-layer LowE film structure as the former has more films than the latter.
To make buildings an energy saver, a higher priority is usually given to efforts to reduce the load on the air-conditioning system than to improving the thermal insulating capability. For reducing the air-conditioning system load, there have been widely used heat reflecting glass panels which include one or more layers of a metal oxide, a metal, and a metal nitride on a transparent glass sheet. Such conventional heat reflecting glass panels are highly effective to reduce the air-conditioning system load because they has as good sunlight shielding performance as the triple-Ag-layer LowE film structure.
The sunlight shielding performance of each of the glass panel with the single-Ag-layer LowE film structure and the glass panel with the double-Ag -layer LowE film structure is poorer than the sunlight shielding performance of the conventional heat reflecting glass panels. Therefore, when a multilayer glass pane using a glass panel with the single-Ag-layer LowE film structure or double-Ag-layer LowE film structure are employed as window glass panes, a sunlight-induced rise in the indoor temperature is higher than it is when a heat reflecting glass panel is used as a window glass pane. From the standpoint of the sunlight shielding performance, therefore, it is preferable to use a heat reflecting glass panel as a window glass pane.
However, the visible light transmittance of a heat reflecting glass panel is much lower than the visible light transmittance of a glass panel with the single-Ag-layer LowE film structure, the double-Ag-layer LowE film structure, or the triple-Ag-layer LowE film structure. Therefore, when a heat reflecting glass panel is employed as a window glass pane, the interior room is relatively dark in the daytime, and the window glass pane looks unnatural.
There have already known heat reflecting glass panels that are designed to solve the above problems by reducing the thickness of a metal or metal oxide film for higher visible light transmittance. However, these heat reflecting glass panels with such higher visible light transmittance are necessarily poor in sunlight shielding performance.
The sunlight shielding performance of glass panels with the triple-Ag-layer LowE film structure is of substantially the same level as the sunlight shielding performance of heat reflecting glass panels. However, the glass panels with the triple-Ag-layer LowE film structure are highly expensive to manufacture because of the large number of films, i.e., seven films, required.
It is therefore an object of the present invention to provide a sunlight shielding glass panel which has higher visible light transmittance than the visible light transmittance of conventional heat reflecting glass panels, and also has sunlight shielding performance that is of substantially the same level as the sunlight shielding performance of conventional glass panels with the triple-Ag-layer LowE film structure or conventional heat reflecting glass panels.
Another object of the present invention to provide a sunlight shielding glass panel which has as small a number of films and which is relatively inexpensive to manufacture.
According to the present invention, there is provided a sunlight shielding translucent glass panel comprising a translucent sheet, an absorbing layer disposed on the translucent sheet, at least one composite layer disposed on the absorbing layer, and an upper transparent dielectric film disposed on the composite layer, the at least one composite layer comprising a transparent dielectric film and a mainly Ag film composed mainly of silver which are successively arranged in the order named from the translucent sheet.
The translucent sheet may comprise a glass sheet which is transparent or semitransparent in a visible light wavelength range or a synthetic resin sheet which is transparent or semitransparent in a visible light wavelength range. The glass sheet may be made of float glass, soda-lime glass, borosilicate glass, crystallized glass, or the like. The synthetic resin sheet may be made of PET (polyethylene terephthalate), PVB (polyvinyl butyral), EVA (ethylene-vinyl acetate copolymer), a cellulose resin, or the like. Generally, the translucent sheet may have a thickness which should range preferably from 0.5 to 10 mm, more preferably from 1 to 5 mm.
The absorbing layer, which is capable of absorbing sunlight to a certain extent, should preferably have a visible light transmittance ranging from 45 to 85%, more preferably from 50 to 80%. Preferably, the absorbing layer comprises a layer of metal nitride having a thickness ranging from 2 to 15 nm, preferably from 3 to 12 nm, or a layer of metal (a single metal or an alloy) having a thickness ranging from 0.3 to 2 nm, preferably from 0.5 to 1.8 nm. The metal nitride may comprise at least one selected from the group consisting of titanium nitride, zirconium nitride, tantalum nitride, and chromium nitride. The metal may comprise at least one selected from the group consisting of chromium, an alloy composed mainly of chromium and nickel, stainless steel, an alloy composed mainly of stainless steel, zinc, niobium, titanium, zirconium, and tungsten.
Each of the transparent dielectric film of the composite layer and the upper transparent dielectric film may comprise a single-layer film selected from the group consisting of a zinc oxide film, a tin oxide film, a silicon nitride film, a titanium oxide film, a zinc oxide film doped with aluminum, and a tin oxide film doped with at least one of antimony and fluorine, or may comprise a laminated film composed of a plurality of films each selected from the above group. These films may be made of different materials or some of these films may be made of one material.
The mainly Ag film may comprise an Ag film or an Ag film which is made of silver and preferably 0.1 to 5%, more preferably 0.1 to 4%, of at least one material selected from the group consisting of palladium, gold, indium, zinc, and tin. The mainly Ag film may have a thickness which should range preferably from 7.5 to 18 nm, and more preferably from 10 to 15 nm.
A protective layer made of titanium oxide or silicon nitride and having a thickness which should range preferably from 5 to 30 nm, more preferably from 10 to 20 nm, may be disposed on a surface of the upper transparent dielectric film remote from the composite layer.
The at least one composite layer may include an additional layer disposed on one or both surfaces of the mainly Ag film. The additional layer may be made of at least one selected from the group consisting of chromium, an alloy composed mainly of chromium and nickel, stainless steel, an alloy composed mainly of stainless steel, zinc, niobium, titanium, zirconium, and tungsten. The additional layer is effective to increase the heat resistance of the mainly Ag film, and also to prevent the mainly Ag film from being oxidized when the transparent dielectric film is grown on the mainly Ag film in an atmosphere containing oxygen. Therefore, the mainly Ag film is effectively prevented from being peeled off due to corrosion, by the additional layer. The additional layer should preferably have a thickness ranging from 0.5 to 3 nm, and more preferably from 0.8 to 1.5 nm.
The at least one composite layer may comprise a first composite layer and a second composite layer which are successively arranged in the order named from the translucent sheet. The mainly Ag films of the first and second composite layers should preferably have a combined thickness ranging from 20 to 30 nm, more preferably 23 to 27 nm. The sunlight shielding translucent glass panel should preferably have a visible light transmittance ranging from 45 to 65%, more preferably from 55 to 65%. The sunlight shielding translucent glass panel should preferably have a sunlight transmittance ranging from 20 to 35%, more preferably from 20 to 30%. In order for the sunlight shielding translucent glass panel to reflect or pass light whose color looks as natural as possible, the transparent dielectric film of the first composite layer should preferably have a thickness ranging from 25 to 50 nm, more preferably 30 to 45 nm, the transparent dielectric film of the second composite layer should preferably have a thickness ranging from 60 to 100 nm, more preferably from 70 to 90 nm, and the upper transparent dielectric film should preferably have a thickness ranging from 30 to 45 nm, more preferably from 34 to 40 nm.
According to the present invention, there is also provided a sunlight shielding translucent multilayer glass panel assembly comprising a sunlight shielding translucent glass panel as described above, and at least one second translucent sheet disposed in confronting relation to the sunlight shielding translucent glass panel. The sunlight shielding translucent glass panel and the at least one second translucent sheet are fixed to each other such that the absorbing layer, the composite layer, and the upper transparent dielectric film are interposed between the translucent sheet of the sunlight shielding translucent glass panel and the at least one second translucent sheet. The second translucent sheet may be made of any of the materials and may have any of the thicknesses which have been referred to above with respect to the translucent sheet of the sunlight shielding translucent glass panel. The second translucent sheet may have a second multilayer film which may be identical to the multilayer film on the translucent sheet of the sunlight shielding translucent glass panel. The second multilayer film should preferably be interposed between the second translucent sheet and the translucent sheet of the sunlight shielding translucent glass panel or another second translucent sheet.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.